Correlation between ultrasonic velocity and solutionising time in Rene 80 superalloy

Abstract

Ultrasonic measurements have been used to characterise the solutionising phenomenon in Rene 80, a Ni based superalloy. Starting material was solutionised at 1204°C for 30–120 min on identical samples. The microstructures of these samples were evaluated by ultrasonic immersion technique, X-ray diffraction and scanning electron microscopy. It was observed that the area fractions and, consequently, the γ′ volume fractions were decreased by increasing the solutionising time. A direct correlation was observed between ultrasonic wave velocity and solutionising time at 1204°C. The ultrasonic compression wave velocity followed a descending pattern similar to that of γ′ area fraction with the increase in solutionising time. The observed variation in ultrasonic velocity has been attributed to the effect of the γ′ dissolution on the elastic constants of the material.